| Objective To optimize the parameters and establish a standard imaging protocol for high-resolution MR imaging of the olfactory system. Methods Ten normal volunteers underwent high-resolution MR examination. The protocol included routine axial T2W, axial FLAIR, 3D-SPGR, high-resolution coronal T2W and T1W as well as high-resolution sagittal T2W sequences. The image quality of images acquired with quadrature and 8-channel coils was compared. And the image quality and contrast of T1W images acquired with IR and SE sequences were also compared. The demonstration of olfactory bulbs, olfactory tracts and olfactory cortex was visualized and recorded. Results The signal noise ratios(SNR) of images acquired with 8-channel coil were higher than those acquired with quadrature coil(P<0.05). The susceptibility artifact was more dominant on SE sequence T1W images than IR sequence. But the contrast for olfactory bulbs and tracts was not significant different on these two sequences(P>0.05). The olfactory bulbs, olfactory tracts and olfactory cortex can be clearly depicted on high-resolution MR images. Conclusions The standard protocol for high-resolution MR imaging of olfactory system should include axial T2W, axial FLAIR, 3D-SPGR, high-resolution coronal T2W and IR T1W as well as sagittal T2W sequences with 8-channel coil. And this protocol is suitable for MR imaging of dysosmic patients caused by congenital, post-trauma and neurodegenerative diseases. Objective To study the MR imaging findings of congenital dysosmia. Methods Forty-seven patients with congenital dysosmia and 21 normal volunteers underwent MRI examination. Among the 47 patiens, patients with Kallmann syndrome accounted for 83.0% and patients with isolated dysosmia for 17.0%. The features of congenital malformation were recorded. The volume of olfactory bulbs, depth of olfactory sulci and diameters of pituitary gland and stalk were measured and compared. Results All the patients had abnormal findings in olfactory bulbs and tracts. No abnormal features were found in cortex except for a malacia lesion in inferior frontal lobe in 1 case. The patterns of congenital malformation of olfactory bulbs and tracts included dysplasia of olfactory bulbs and tracts, olfactory bulb hypoplasia with dysplasia of olfactory tract, olfactory bulb dysplasia with existent olfactory tract and olfactory bulb hypoplasia with existent olfactory tract. The imaging findings may be asymmetric in bilateral sides. Patients with dysplasia of olfactory bulbs and tracts accounted for 79.5% of all the patients with Kallmann syndrome. The ratio of dysplasia of olfactory bulbs and tracts in Kallmann syndrome was higher than that in isolated dysosmia(P<0.05). And the olfactory bulbs' volume of patients with Kallmann syndrome was smaller than that of patients with isolated dysosmia(P<0.05). The olfactory sulci were hypoplastic in congenital dysosmic patients. The sulci were shallower in congenital dysosmic patients than those in volunteers(P<0.05). The pituitary gland was smaller and the stalk was thinner in patients with Kallmann syndrome than volunteers(P<0.05). Conclusions The malformations of congenital dysosmic patients are located in olfactory bulbs and tracts, not in olfactory cortex. Dysplasia or hypoplasia of olfactory bulbs, tracts and sulci can be depicted on MR images. And dysplasia of olfactory bulbs and tracts is the most common findings. Small pituitary gland and thin stalk can also be found in patients with Kallmann syndrome. MR imaging can make definite diagnosis of congenital dysosmia and be valuable for clinical diagnosis and treatment. Objective To evaluate the value of high-resolution MR imaging for diagnosis of post-trauma dysosmia. Methods Twenty-eight patients with post-trauma dysosmia underwent MR examination. The injury of olfactory bulbs, tracts and cortex was visualized and recorded. And the volume of olfactory bulb in dysosmic patients was measured and compared with 15 normal volunteers. Results Seventeen of 28 patients had primary injury at occipital area. The imaging finding mostly manifested as malacia and chronic hemorrhagic foci. The injuries were commonly located at frontal lobes(92.9%), olfactory bulbs and tracts(82.1%) as well as temporal lobes(42.9%). The olfactory bulbs in dysosmic patients were smaller than volunteers(P<0.05). Conclusions The most common primary injury location for post-traumatic dysosmia is occipital area. The imaging findings of post-trauma dysosmia commonly manifest as malacia and chronic hemorrhageic foci in frontal lobe, olfactory bulbs and tracts as well as temporal lobes. For clearly depicting lesions in these areas, high-resolution coronal images are necessary. MR images are sensitive to the injury foci and can be complementary modality for diagnosis of post-traumatic dysosmia. Objective To explore whether the olfactory bulbs' volume in Parkinson's disease(PD) patients is different from normal aging persons and whether the change of volume can be valuable for clinical diagnosis. Methods The olfactory bulbs' volume of 36 PD patients, 9 parkinsonism(PDS) patients, 94 aging normal volunteers and 21 young normal volunteers was measured. And 31 PD patients, 7 PDS patients and all the aging volunteers underwent subjective olfactory test and OERP examination. The subjective identification thresholds, P2 latency and olfactory bulbs' volume were compared among groups. The diagnostic value of those modalities was evaluated. Results The PD and PDS patients had higher identification thresholds, longer P2 latency and smaller olfactory bulbs than aging volunteers(P<0.05). These values showed no correlation with duration of disease(P>0.05). The area under ROC curve of P2 latency for discriminating PD and normal aging was 0.750 for all age group. For people under age of 59, the area under ROC curve of small olfactory bulbs' volume was 0.728 and of large olfactory bulbs' volume was 0.773. For people under age of 59, the measurement of olfactory bulbs' volume had higher specificity than P2 latency(P<0.05), and was more valuable for discriminating normal aging and PD. Conclusions PD patients are hyposmic. The P2 latency can be diagnostic modality for PD with high sensitivity and relative low specificity. For people under age of 59, measurement of olfactory bulbs' volume has moderate diagnostic value for discriminating PD and normal aging with higher specificity, especially the large olfactory bulbs' volume. Objective To explore whether the olfactory bulbs' volume in Alzheimer's disease(AD) and mild cognitive impairment(MCI) patients is different from normal aging persons and whether the volume change can be valuable for clinical diagnosis. Methods The olfactory bulbs' volume of 14 AD patients, 8 MCI patients, 9 vascular dementia(VD) patients and 94 normal aging volunteers as well as 36 PD patients was measured. Five AD, 5 MCI, 5 VD patients and all the volunteers underwent subjective olfactory test and OERP examination. And the hippocampal volume of AD, MCI patients and volunteers was measured. The identification thresholds, P2 latency and olfactory bulbs' volume were compared among groups. The diagnostic value of measurement of olfactory bulbs' and hippocampal volume was compared. Results AD patients had higher identification thresholds and longer P2 latency(P<0.05). AD and VD patients had smaller olfactory bulb than normal aging persons(P<0.05), but the olfactory bulbs' volume of MCI patients was not significant different from that of normal aging persons(P>0.05). The shrinkage of olfactory bulb showed no correlation with duration of disease and MMSE scores(P>0.05). AD patients had smaller olfactory bulbs than PD patients(P<0.05). The areas under ROC curves of large olfactory bulbs' volume for discriminating normal aging and AD as well as MCI and AD are 0.836 and 0.830 respectively. Combination of measurement of hippocampal and olfactory bulbs' volume may promote discrimination power between normal aging and AD. For discriminating MCI and AD, large olfactory bulbs' volume was more valuable. Conclusions AD patients are hyposmic. AD patients have smaller olfactory bulb than normal aging persons and MCI patients. And the extent of olfactory bulb shrinkage in AD patients is greater than that in PD patients. Combination of measurement of hippocampal and olfactory bulbs' volume can promote discrimination power between normal aging and AD. And for predicting conversion from MCI to AD, large olfactory bulbs' volume is more valuable. Objective To explore the feasibility of olfaction fMR imaging with modified OEP-98C olfactometer and event-related design. Methods Six young right-handed men underwent olfaction fMR imaging with event-related design. OEP-98C olfactometer was modified to accommodate MR environment. Isoamyl acetate and vanillin were chosen as pure olfactory nerve stimulator. There were 2 types of tasks in the experiment. In 1 task, only isoamyl acetate was used as odorant. In the other task, to avoid possible decreased olfactory attention, vanillin was given before each presentation of isoamyl acetate. Results In both tasks, uniform activation in piriform cortex and secondary olfactory cortex was determined. But activation at left medial orbitofrontal lobe, right amygdala, bilateral hippocampi and anterior cingulate gyri was different in the 2 tasks(P<0.01). Conclusions With isoamyl acetate as odorant, modified OEP-98C olfactometer, short TE and event-related design, olfaction fMR imaging can depict cortex activation at primary and secondary olfactory cortex. Applying other odorant with similar quality to avoid olfactory attention decrease can not promote depiction of activation in primary olfactory cortex. |
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